It is known to engage a doctor blade at an inclination with respect to the axis of a roller or cylinder of a printing machine, especially if the roller or cylinder includes a gap or groove to clamp a cover thereover, for example the ends of a printing plate. Locating the doctor blade at an angle facilitates sliding of the doctor blade over the gap or groove. This is explained in the cited literature, "Der Tiefdruck" ("Gravure Printing") by Braun, 1952, p. 139.
When engaging a doctor blade against a cylinder, at an angle with respect to the cylinder axis when the doctor blade is held in the usual holder arrangements, the doctor blade has the tendency to become wavy or to undulate, especially when it is tried to engage the doctor blade over its entire length against the cylinder. The tendency to waviness or undulation increases with the inclination angle of the doctor blade with respect to the axis of the cylinder. The formation of waves or undulations makes the engagement pressure of the blade against the cylinder non-uniform over the length of the blade. If it is tried to so tightly engage the doctor blade against the cylinder that the required minimum engagement pressure is available at any position, then some locations of the blade are more tightly engaged than others, thus causing increased wear on the doctor blade and/or the cylinder.